Casting processes are frequently used to produce cast articles having a complex geometry. Precision sand casting is one such casting process used for producing cast articles having complex geometries. The casting articles typically require optimized mechanical properties and dimensional precision. Castings formed using precision sand casting are formed by pouring a molten material, such as molten metal, into a mold cavity formed from sand. The mold cavity is formed by placing a duplicate of the desired casting, referred to as a pattern, into a casting mold. The casting mold is then filled with packed sand around the pattern. The casting mold is closed around the pattern and then reopened. The pattern is removed to result in a mold cavity being formed in the packed sand having the shape of the pattern. Once the sand is allowed to dry, the casting mold is prepared to receive the molten metal.
Cast articles having transitions from a thick portion to a thin portion, extensive horizontal or flat surfaces, and sharp corners, are susceptible to defects. Such defects are formed in the casting due to a turbulent flow of molten metal when the mold cavity is filled, and an uneven distribution of the molten metal through the mold cavity. To militate against turbulent flow, the flow-rate of the molten metal into the mold cavity may be regulated. For example, as the volume of the mold cavity increases, the flow-rate of the molten metal may be adjusted to militate against the solidification of the metal in the mold, thereby impeding the flow of additional molten metal to the mold cavity. Conversely, if a molten material is caused to flow into the mold cavity at a high flow rate to fill a large cavity and the volume of the cavity then decreases, a back-pressure may be created within the mold. It is understood that the mold fill rate may be constant even if the mold cross-section varies.
Because the mold cavity is formed by the packed sand and enclosed in the casting mold, it may be difficult to determine a location of the molten material within the mold at a given time. Furthermore, parameters such as a flow-rate, a melt temperature, a pressure tightness, and atmospheric pressure may vary from one casting operation to the next. Current sand casting processes use thermocouples or contact probes in an attempt to monitor the position of a molten metal front. The thermocouples or probes must be disposed within the casting mold and in contact with the casting, which may influence the quality of the casting.
It would be desirable to develop a non-invasive, real-time, molten metal level sensing system and method for determining the level of a molten metal within the mold, wherein contact with the molten metal or the casting mold is militated against.